var supportOrientation = (typeof window.orientation === 'number' &&
    typeof window.onorientationchange === 'object');

var init = function () {
    var htmlNode = document.body,
        orientation;
    // var htmlNode = document.body.parentNode,
    //     orientation;
    var updateOrientation = function () {
        if (supportOrientation) {
            orientation = window.orientation;
            switch (orientation) {
                case 90:
                case -90:
                    orientation = 'landscape';
                    break;
                default:
                    orientation = 'portrait';
                    break;
            }
        } else {
            orientation = (window.innerWidth > window.innerHeight) ? 'landscape' : 'portrait';
        }
        htmlNode.setAttribute('class', orientation);
    };

    if (supportOrientation) {
        window.addEventListener('orientationchange', updateOrientation, false);
    } else {
        //监听resize事件
        window.addEventListener('resize', updateOrientation, false);
    }

    updateOrientation();
};

window.addEventListener('DOMContentLoaded', init, false);

